# std::destroy

From cppreference.com
< cpp‎ | memory

Defined in header `<memory>` |  |
| (1) |
template< class ForwardIt > void destroy( ForwardIt first, ForwardIt last ); |  | (since C++17) (until C++20)
template< class ForwardIt > constexpr void destroy( ForwardIt first, ForwardIt last ); |  | (since C++20)
template< class ExecutionPolicy, class ForwardIt > void destroy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last ); | (2) | (since C++17)

1) Destroys the objects in the range `[`first`,` last`)`, as if by

    for (; first != last; ++first)
        std::destroy_at(std::addressof(*first));

2) Same as (1), but executed according to policy. This overload participates in overload resolution only if all following conditions are satisfied:

std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true. | (until C++20)
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> is true. | (since C++20)

### Parameters

first, last | - | the range of elements to destroy
policy | - | the execution policy to use
Type requirements
- `ForwardIt` must meet the requirements of LegacyForwardIterator.
- No increment, assignment, comparison, or indirection through valid instances of `ForwardIt` may throw exceptions.

### Return value

(none)

### Complexity

Linear in the distance between first and last.

### Exceptions

The overload with a template parameter named `ExecutionPolicy` reports errors as follows:

- If execution of a function invoked as part of the algorithm throws an exception and `ExecutionPolicy` is one of the standard policies, std::terminate is called. For any other `ExecutionPolicy`, the behavior is implementation-defined.
- If the algorithm fails to allocate memory, std::bad_alloc is thrown.

### Possible implementation

    template<class ForwardIt>
    constexpr // since C++20
    void destroy(ForwardIt first, ForwardIt last)
    {
        for (; first != last; ++first)
            std::destroy_at(std::addressof(*first));
    }

### Example

The following example demonstrates how to use `destroy` to destroy a contiguous sequence of elements.

Run this code

    #include <iostream>
    #include <memory>
    #include <new>

    struct Tracer
    {
        int value;
        ~Tracer() { std::cout << value << " destructed\n"; }
    };

    int main()
    {
        alignas(Tracer) unsigned char buffer[sizeof(Tracer) * 8];

        for (int i = 0; i < 8; ++i)
            new(buffer + sizeof(Tracer) * i) Tracer{i}; //manually construct objects

        auto ptr = std::launder(reinterpret_cast<Tracer*>(buffer));

        std::destroy(ptr, ptr + 8);
    }

Output:

    0 destructed
    1 destructed
    2 destructed
    3 destructed
    4 destructed
    5 destructed
    6 destructed
    7 destructed

### See also

destroy_n (C++17) | destroys a number of objects in a range (function template)
destroy_at (C++17) | destroys an object at a given address (function template)
ranges::destroy (C++20) | destroys a range of objects (algorithm function object)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/memory/destroy&oldid=153302"